Is Iowa a rival to Nebraska? Kind of. It's getting there. Look, it's never going to perfect like Oklahoma was. We just need to accept that Nebraska will never have another Oklahoma again.
I can come up with a scenario that essentially would make the two full-blooded rivals for the next decade. It will only to take two games over the next year and one week.
2018 game next week: Nebraska comes out and pummels Iowa like they did to Colorado in 2005. Nebraska scores late, goes for two and gets it. Nebraska beats Iowa in Iowa City 46-14. Most Nebraska fans mock Iowa after the thrashing and say Iowa may never beat Nebraska again.
2019 game in a year and one week: Nebraska enters at 9-2 and ranked around the top 10. Iowa enters at 7-4 enduring a standard Kirk Ferentz ho-hum year. Nebraska would clinch the west division with a win. They don't win though. Iowa rolls into Lincoln and stuns Nebraska 24-20 after the Hawkeye D has a goal line stand in the final minutes to preserve the win. Iowa fans mock Nebraska about how they failed to win the division again and that they never will again.
This scenario makes Iowa the biggest rival for most Nebraska fans for the immediate future. Not forever. but for at least a while. And the more games like the two above and the further entrenched they become as rivals.

/channeling my inner J.R. voice
"Oh my God! Harbaugh is turning on Frost! He just nailed him with a steel chair! Frost is done for. He just got his head split in half!"
/Harbaugh attempts to pin Frost, but Frost kicks out at 2
"By God! Frost kicked out! He kicked out! That's instinct! He's just going on instinct right now!"
/the Michigan State fight song plays
"Wait a minute. No, it can't be! That's Mark Dantonio's music! The only man that hates Harbaugh more than Frost right now!"
/Dantonio nails Harbaugh with a chair shot as Frost stumbles to his feet
"Oh God! That sickening thud of a steel chair shot to the head! And Frost has Harbaugh in his cross hairs now!"
/Frost sizes up Harbaugh as Jim slowly rises to his feet, then Frost hits the spear
"By God! Frost just split him in half! It's elementary now!"
/Frost pins Harbaugh for the three count
"Frost wins! Frost wins! Harbaugh's plan backfired horrendously! Now he's made an enemy for life. We'll see if he continues to attack each day with an enthusiasm unknown to mankind now. And I don't know if this unholy alliance between Dantonio and Frost will last, but for at least one night, they gave Harbaugh what he deserved."

I suppose you could do it. There would be a few logistical problems/hurdles to clear.
1) It wouldn't be an official NCAA game, so technically the NCAA could dole out punishments for competing in an unsanctioned game.
2) Since it isn't an official NCAA game, you'd need someone to pay for all the officials, chain gang, instant replay crew, etc. The tickets may pay for that, but ...
3) How many Nebraska fans would you expect to go? Because whatever number that is, that would be the total number for paid attendance. I don't think Florida State fans would go this year even if the tickets were free. They want to forget this year.
4) You'd have to convince both teams and staffs to do it. Nebraska may want to do it because they look much better now than in Sepetember. I doubt Florida State players would want to play.
5) Similar to point 1, any practices Nebraska had would be illegal since they won't be bowl eligible. Practicing could lead to minor sanctions. If the game was somehow allowed, neither team would be allowed to practice ahead of time.
In all honesty though, I'd watch it if it somehow happened. Apologies if I sound like a wet blanket. It's an interesting idea.

I don't know if Arkansas-Pinebluff is LITERALLY the worst team in division 1 football, but if they aren't they appear to be pretty damn close.
I also don't know if they have had any games cancelled, but they appear to really suck.

It looks like Nebraska will struggle this year. I've never really had any love for the Big 10. I guess I just want to watch the (college football) world burn this year.
I hope Wisconsin, Iowa, Northwestern, Ohio State, Penn State, Michigan and Michigan State lose every game the rest of the year. I realize they can't because they play each other. Don't care.

I agree with everyone that the top three in the East will be some order of Ohio State, Penn State and Michigan.
Who the heck knows in the West? I suppose Iowa and Wisconsin will be and Illinois definitely won't.
I'll say:
East
1) Penn State
2) Ohio State
3) Michigan
West
1) Iowa
2) Wisconsin
3) Ummm ... Northwestern? Maybe Nebraska?

Nick Saban and Alabama lost to Lousiana-Monroe in 2007, his first year at Alabama. And unlike Troy who may win 9 or 10 games this year, Monroe went just 6-6 and did not play in a bowl game.
I'm not saying Frost will have Saban's success, but let's not be stupid. Year one. Backup walkon QB.

If I was a betting man, I'd say that Nebraska will play Tennessee State Oct. 27. Tennessee State is really bad and would almost certainly be the worst team Nebraska has played since Idaho State in 2012.
That may seem dirty or distasteful, but Nebraska is going to schedule a win. If not an FCS team, then ECU would probably work too. It won't be UCF. Zero chance this year. Maybe in 2022 when all the players Frost recruited are gone.

Art Briles is a terrible and awful person, but was a really good coach at Baylor. A few years ago, I think 2013 or 2014, Baylor lost all their QBs to injury before a bowl game against North Carolina.
Baylor shifted their offense to more of a single-wing veer offense and put a really good athlete at QB. They then ran it almost every play against UNC and destroyed them.
Obviously this isn't the same scenario. Nebraska doesn't have a month before its next game and the Huskers don't have top-10 talent. If Martinez is out for a while though and Bunch goes down with an injury, then they may have to try something like this.